EDIT - The original site is now dead, it seems, but I found another superb resource on pre-Roman sites. IT's very comprehensive, and although the focus is on Megalithic sites across the UK, some other ancient sites are covered. The interactive map takes a while to load - and maybe to get used to - but it erally is a great feature: Modern Antiquarian - Map of Sites
I'm actually tempted to start taking the family out this summer, and go around a few of these sites - many of which I'd not even heard of. It could be a good idea to to take photos, and maybe write up something about them for the Chronicles site. Hm...
I'm collecting together some very decent ones on Roman Britain. Went to Cawthorn Roman forts the other day. Great day out. Hence why I'm collecting some Rome resources.
You are ineed lucky to have all those ancient ruins over there in Britain. I will use your link to eye some places for when I fly over the pond to visit one day.
Just to say I've edited the original post - check out the link for a great guide to Megalithic UK sites.